The field problem
Missing Down-Conductor Route on One Side of a High-Rise Tower
field problem
High-rise building: down-conductor routes were omitted from one complete façade because of curtain-wall, cladding, architectural and MEP coordination conflicts. Lightning-current paths remained on only three sides.
why pis rejected the arrangement
Omitting one side can create less balanced current sharing, longer current paths, higher local potential differences and magnetic coupling, increased side-flash/internal surge risk, greater separation-distance demands in some areas and uneven loading of bonding/earthing points. Heating is not stated as an inevitable outcome; it depends on current, specific energy, material, cross-section, joint quality and current sharing.
Why it failed
Why PIS Rejected the Arrangement
Omitting one side can create less balanced current sharing, longer current paths, higher local potential differences and magnetic coupling, increased side-flash/internal surge risk, greater separation-distance demands in some areas and uneven loading of bonding/earthing points. Heating is not stated as an inevitable outcome; it depends on current, specific energy, material, cross-section, joint quality and current sharing.
Failure Scenario
One façade omitted -> conductors concentrated on three sides -> longer/less balanced lightning-current paths -> higher potential differences and magnetic coupling -> increased side-flash and internal surge risk -> greater stress on façade components and critical systems.
Follow the engineering
Switch between the field condition and the engineering concept. Trace the path and examine what changes.
Inspect the engineering detail
What changes
Maintain the required number/distribution of down conductors and reroute conflicted paths behind curtain wall or cladding, through approved service zones, or through coordinated concealed architectural routes. Concealment must preserve inspectability, maintainability, bonding and a coordinated earth-termination connection.
Correction & verification
Maintain the required number/distribution of down conductors and reroute conflicted paths behind curtain wall or cladding, through approved service zones, or through coordinated concealed architectural routes. Concealment must preserve inspectability, maintainability, bonding and a coordinated earth-termination connection.
Verification recorded in the case
- Lightning-current path review; down-conductor distribution; separation-distance calculation; curtain-wall shop-drawing coordination; continuity testing of natural conductors; bonding verification; pre-cladding inspection; as-built documentation; component compliance; test-joint accessibility.
References & project context
References are reproduced from the PIS casebook. Select the governing edition and project acceptance criteria before using them for a design. The diagrams explain the concept, rather than define construction dimensions.
The supplied case references IEC 62305-3:2024 and IEC 62561 component standards. Exact edition, component category and clause applicability must be verified against the governing project standard before publication.
PIS reviewed field handbook · PIS-CS-028
The engineering lesson
A façade conflict should change the route of the down conductor - not remove the down conductor.
Lightning current must be distributed by engineering design, not by whichever façade has space left.
Take the lesson into your next design review.